I've owned a couple chronographs, both from Shooting Chrony. The 1st, an F1, didn't last too long before a 45acp round put it down. The F1 has the integrated display - bad idea for a couple reasons. The 2nd chronograph was an Alpha Master. This unit survived a number of shootings because I added a "boo-boo" plate to the front. I even shot the sky screen rods off and the chronograph kept on doing its thing. I gave it away. My present chronograph is another Alpha Master - a newer model. Chrony hits the right price point with a product that is pretty robust compared to the competition. And for some reason, Chrony can sell the remote display Alpha-Master for the same price the competition offers an integrated display.
The Alpha-Master remembers one string of 32 shots and displays low, high, average, Extreme Spread and Standard Deviation. I prefer to be able to record a string longer than 10 shots and I don't mind jotting notes on a pad.
The downside to the Shooting Chrony is quality. Sometimes they ship units that aren't calibrated (sensor alignment). I just sent one back to MidwayUSA due to constant "ERR1" messages with copper jacketed bullets and bright cast lead. Black carbon arrows and .22lr worked fine. I definitely recommend buying one from a walk-in store so you can return it without the cost of shipping.
Chronograph accuracy is a simple matter of starting and stopping a counter by the shadow of a bullet. Count the time fine enough over a known distance and you have a pretty accurate measurement. There are setup errors, like shooting over the unit on an angle, or shooting diagonally across the sensors, that can induce some measurement error. But usually that errors is on the order 50fps or less. Sensor design to detect the shadow varies, and I'm sure you get your money's worth with the expensive units. But as long as you are aware of the limitations, the cheap units are every bit as accurate. Point is, that $300 and $100 chronographs give the same accuracy, and accuracy of a $100 unit is plenty good enough for the hand loader.
The Chrony design is sensitive to light direction, and they seem to work best on a slightly overcast day with the sum directly overhead. On clear blue days you must use the sky screens. They will give erratic results in the rain.
The remote display is very nice - I wouldn't own a chronograph without it. It keeps the fragile LCD away from bullets and puts it right next to you for convenience. Also a remote display allows you to put a boo-boo plate in front of the unit to deflect errant rounds.
A chronograph gives you much more than just the velocity of a load. It also gives you insight into your overall reloading process. When you see the ES and SD of a statically significant sample (lets say 20 or more), you see how all the variables in your process come together. In my opinion, reloading without a chronograph is like being deaf and driving a vehicle without a speedometer.
I use mine on a camera tripod. I always try to level the unit to the angle of the shot to avoid low readings. I've attached a simple boo-boo plate to the front. My previous Alpha-Master used a boo-boo plate that allowed it to survive hits from a 38spl, multiple 45acp, and a 44 mag that knocked the tripod down.
I use bamboo kabob skewers ,cut to about 5" long, ends painted white, inserted into the sky screen holes, to create a visual reference for both elevation over the unit as well as front to back alignment. This makes it pretty easy to get consistent readings. Bamboo shears off without damaging the sensors.
I have used metal junction box covers separated by foam, and while they worked, they were heavy and were permanently dented up pretty bad. Now I use circuit board as it is much lighter and I happen to have a lot of it. The following pictures are worth a box of words, so I'll just let you gather some ideas. I will mention that the goal is to deflect if possible and the foam is essential to reduce penetration. The goal is to deflect a bullet, not absorb it. I wont know how well this boo-boo plate design works until I accidently shoot it (see below). A key part of this design is that the top of the boo-boo plate is at least 1" higher than the sensors. This causes the shooter to mentally reference from the top of the plate, which makes it less likely the shot will be at sensor level. The painted bamboo skewers also give a vertical reference to the shooter. Since the human is the problem, (although a friends 44mag had a way too tall front sight), keeping references above the chronograph reduces the likely-hood of a straight-on hit. Obviously somebody with a 2" scope height above bore center line will need to give some thought before they test the boo-boo plate with their 338mag.
One thing about boo-boo plates: make sure it doesn't shadow the first sensor.
The following will give you some ideas on a boo-boo plate design.
12 feet in front of my table with targets at 25yds
The copper-clad board protects the entire front (picture is looking downward a bit and showing the rear sensor)
Table saw blade kerf was just right for the fiber-glass circuit board. The foam is there to compress and allow the boards to angle backwards.
"In theory there is no difference between theory and practice. In practice there is. " - Yogi Berra
Even though I know better. Even though I've already shot 2 other Chrony's. I shot my new Chrony. May it RIP.
Classic right-hander trigger jerk of low and left. The 270gr WFN from my 44 mag nicked the top-left corner, but broke the front sensor. Of course I didn't have my boo-boo plate on it, because "I know what I am doing".
Since I had already killed my $120 piece of equipment, I thought I might as well test my boo-boo plate. After all, I was convinced of it's superiority over the old metal outlet box cover design. So I decided to put a 270gr WFN @1150fps into the boo-boo plate and note the results. The results were enlightening. Obviously my boo-boo concept plate needs a lot of work. The following photos tell the story.